Technical Field
The present disclosure relates to a system and to a corresponding method for measuring the oscillation frequency of an oscillating element in a MEMS (Micro-Electro-Mechanical System) sensor.
Description of the Related Art
As is known, several MEMS sensors include mobile elements, which, during operation, undergo oscillating movements.
For example, known MEMS accelerometers, gyroscopes and microphones include mobile elements (e.g., in the form of beams or cantilevers suspended via a spring arrangement), which may vibrate at an oscillation frequency.
In particular, a passive vibration motion of a mobile element may be generated by an external acceleration (e.g., a shock), and properties of this vibration motion may be studied to measure the external acceleration or other physical properties of the external environment.
An active vibration of the mobile element may also be generated and maintained, by means of external electrical impulses, so as to detect other physical properties, e.g., a rotation due to the Coriolis principle (e.g., in a gyroscope), or a modification of the resonance frequency (e.g., in a resonant accelerometer).
The oscillating frequency of the mobile element may also change according to the chemical composition, pressure and density of a surrounding environmental medium; accordingly, properties of the oscillating motion may also be used in order to detect chemical parameters of the surrounding medium.
Effective use of a measure of the oscillating frequency of the mobile element is however difficult to implement, since a very fast and sensitive measuring system is used in order to measure the very high values of the same oscillating frequency.
For example, a capacitive coupling scheme has been proposed in known MEMS sensors, between the mobile element (usually denoted as “rotor” element) and one or more corresponding fixed elements (usually denoted as “stator” elements). The electrical signal, indicative of the capacitive variation, is detected and processed to measure the oscillating frequency.
However, this solution does not prove to be completely satisfactory, in terms of its response time and sensitivity.